Method for the emergency shutdown of a bus system, and bus system

ABSTRACT

In a method for the emergency shutdown of a bus system, and a bus system, having a master module and bus subscribers disposed in series, the master module and the bus subscribers sending data packets to one another with the aid of a data line, the method has the temporally consecutive method steps: in a first method step, a bus subscriber and/or the master module detect(s) an error status, in a second method step, the bus subscriber and/or the master module send(s) an emergency signal to all bus subscribers and to the master module, in a third method step, a further bus subscriber receives the emergency signal, immediately forwards it to an adjacent bus subscriber and simultaneously evaluates it, and in a fourth method step, the further bus subscriber shuts itself down automatically.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/098,498, which is the national stage of PCT/EP2017/025057,having an international filing date of Mar. 23, 2017, and claimspriority to Application No. 102016005314.3, filed in the FederalRepublic of Germany on May 2, 2016, each of which is expresslyincorporated herein in its entirety by reference thereto.

FIELD OF THE INVENTION

The present invention relates to a method for the emergency shutdown ofa bus system, and to a bus system.

BACKGROUND INFORMATION

German Published Patent Application No. 10 2008 022 655 describes amethod for the secure operation and/or for the secure shutdown of anelectrical device.

SUMMARY

Example embodiments of the present invention provide a method for theemergency shutdown of a bus system, and a bus system, which offer bettersecurity.

According to an example embodiment of the present invention, a methodfor the emergency shutdown of a bus system having a master module andbus subscribers disposed in series, the master module and the bussubscribers sending data packets to one another with the aid of a dataline, includes the temporally successive method steps: in a first methodstep, a bus subscriber and/or the master module detect(s) an errorstatus, in a second method step, the bus subscriber and/or the mastermodule transmit(s) an emergency signal to all bus subscribers and to themaster module, in a third method step, a further bus subscriber receivesthe emergency signal, immediately forwards it to an adjacent bussubscriber and simultaneously evaluates it, and in a fourth method step,the further bus subscriber shuts itself down.

This has the advantage that all bus subscribers of the bus system areable to be shut down within a short period of time. The emergency signalis, for example, not fully evaluated right away but instead issimultaneously forwarded to all bus subscribers and to the master moduleas soon as it has been identified as an emergency signal.

The emergency signal may interrupt a data packet. This has the advantagethat the emergency signal is immediately sent to all bus subscribers andto the master module as soon as the error status has been identified.There may be no need to wait until the data packet has been transmittedin its entirety. As a result, a rapid shutdown of all bus subscribers ispossible, and the security is improved.

The transmission of the interrupted data packet may not be continued andthe interrupted data packet may be discarded. This has the advantagethat an error that occurs in the data packet due to the interruption hasno effect on the bus system. The security is therefore improved.

All data packets may have an identical length, in particular signallength, and the length of the emergency signal, in particular the signallength, may be shorter than the length of the data packets. This has theadvantage that the emergency signal is able to be transmitted fasterthan a data packet. As a result, the security is improved.

Two consecutive data packets may be temporally spaced apart from eachother by a transmission pause, and the emergency signal may interrupt atransmission pause. This has the advantage that the emergency signal isable to be transmitted immediately and independently of the status ofthe data line. The emergency signal may be transmittable at any time,regardless of whether a data packet happens to be transmitted or atransmission pause exists at the time when the emergency signal istransmitted.

The emergency signal may be shorter than the transmission pause.

The bus system may have two data lines, the bus subscriber and/or themaster module transmitting the emergency signal simultaneously with theaid of both data lines. This has the advantage that the emergency signalreaches all bus subscribers in a communications ring faster when it istransmitted with the aid of the two data lines in two oppositedirections than when the emergency signal is transmitted by only onedata line in one direction.

The following temporally successive method steps may be carried out forthe initialization of the bus system: in an initial method step, themaster module asks the bus subscribers to log in to the master module,in a following method step, a first bus subscriber disposed downstreamfrom the master module logs in to the master module, in a further methodstep, the first bus subscriber waits for a predefined period of time tosee whether a second bus subscriber downstream from the first bussubscriber logs in to the master module, in a following method step, thefirst bus subscriber closes the bus system if no second bus subscriberlogs in to the master module within the predefined period of time, or ina following, in particular an alternative, method step, a second bussubscriber logs in to the master module within the predefined period oftime and waits a further predefined period of time to see whether athird bus subscriber disposed downstream from the second bus subscriberlogs in to the master module, and the second bus subscriber closes thebus system if no third bus subscriber logs in to the master modulewithin the further predefined period of time.

This has the advantage that the bus system automatically initializesitself with the aid of the present method. The bus system recognizeswhich one is the bus subscriber most remote from the master module andthis bus subscriber automatically closes the bus system. An operator ofthe bus system is thereby relieved because there is no need to connect aterminating impedance within the system. This improves the security.

The predefined periods of time may be adaptable to the bus subscribers,so that there is a sufficient wait to allow a bus subscriber that needsa longer period of time for the activation to log in securely as well.

A fourth bus subscriber disposed downstream from the first bussubscriber and/or the second bus subscriber may send a login to themaster module in a further method step after all predefined time periodshave elapsed, and in a sixth method step, the first bus subscriberand/or the second bus subscriber may open the bus system and may forwardthe log in of the fourth bus subscriber to the master module. This hasthe advantage that a bus subscriber that requires a longer period oftime for the activation is easily able to be logged in retroactively.

A release may be granted to the bus system in an alternative furthermethod step, in particular by a control superordinate to the mastermodule. This has the advantage that through the release, the bus systemobtains an external release in an additional method step after asuccessful initialization. Only after the release does the bus systemtransition to a production mode in which the bus subscribers areactuated by the master module.

A fourth bus subscriber disposed downstream from the first bussubscriber and/or the second bus subscriber may send a login to themaster module in a subsequent method step after all predefined periodsof time have elapsed, and in a seventh method step, the first bussubscriber or the second bus subscriber may block the login of thefourth bus subscriber to the master module. This has the advantage thatno bus subscriber is admitted to the bus system in the production mode,i.e. after the granted release. The admittance to the bus system may beblocked with the aid of an upstream bus subscriber so that the mastermodule is relieved. This increases the security.

The release of the bus system may be revoked in a subsequent methodstep, in particular by a control superordinate to the master module, andin a subsequent method step, the first bus subscriber or the second bussubscriber may forward the login of the fourth bus subscriber to themaster module. This has the advantage that the fourth bus subscriber isautomatically admitted to the bus system in a new startup of the bussystem.

In a further method step, the fourth bus subscriber may wait for apredefined period of time to see whether a bus subscriber downstreamfrom the fourth bus subscriber logs in to the master module, and in asubsequent method step, the fourth bus subscriber may close the bussystem if no bus subscriber disposed downstream from the fourth bussubscriber logs in to the master module within the predefined period oftime. This has the advantage that when a late bus subscriber, inparticular the fourth bus subscriber, logs in to the bus system, thisbus subscriber itself checks whether it is the most remote bussubscriber from the master module, in particular the last bussubscriber, and closes the bus system as the case may be.

The following temporally successive method steps may be carried out forthe allocation of addresses to the bus subscribers: in one method step,the master module allocates a first address to a first bus subscriberand transmits this first address to the first bus subscriber, the firstaddress in particular being a natural number n, the first address inparticular being 0 or 1, in a following method step, the first bussubscriber increments the first address by one and allocates it to asecond bus subscriber as the second address and transmits this secondaddress to the second bus subscriber, the second address in particularbeing the natural number (n+1), and in a further method step, the secondbus subscriber logs in to the master module with its second address.

This has the advantage that the assignment of the addresses to the bussubscribers takes place automatically. As a result, the initializationof the bus system is able to be executed in a secure and rapid manner.

During the addressing, a data packet may pass an inactive bus subscriberso that the next active bus subscriber of the bus system receives theaddress and uses it to log in to the master module.

In a following method step, the second bus subscriber may increment thesecond address by one, may allocate this address to a third bussubscriber as the third address, and may transmit this third address tothe third bus subscriber, the third address in particular being thenatural number (n+2), and in a further method step, the third bussubscriber may login to the master module using its third address. Thishas the advantage that each bus subscriber, in particular each activebus subscriber, is automatically able to be addressed with the aid ofthe present method.

The address m may be allocated to an m^(th) bus subscriber in a furthermethod step, and the m^(th) bus subscriber may log in to the mastermodule using the address m, m being a natural number, and m inparticular being unequal to n, m in particular being equal to 15, andthe m^(th) bus subscriber may allocate the address m to a bus subscriberdownstream from the m^(th) bus subscriber, and may transmit the addressm to the downstream bus subscriber, the m^(th) bus subscriber inparticular not incrementing the address, and (m−1) being the maximallypossible number of bus subscribers in the bus system. This has theadvantage that the number of bus subscribers is able to be limited. Datapackets do not become too long in this manner, and the transmissionspeed is improved. The number of bus subscribers may be automaticallyrestricted.

The master module may abort the method and may transmit an error reportwhen a bus subscriber using the address m logs into the master module.This has the advantage that the bus system automatically recognizes whentoo many bus subscribers are logging in. The error report may be sent toa superordinate control. The master module may generate a warningsignal, in particular a warning tone or a warning light.

According to an example embodiment of the present invention, a bussystem is able to be shut down with the aid of a method for the shutdownof a bus system as previously described, and the bus system has a mastermodule and bus subscribers, which are disposed in series, the mastermodule and the bus subscribers being connected to one another with theaid of at least one data line.

This has the advantage that the bus system is able to be shut downsecurely and rapidly with the aid of the present method. The emergencysignal may be simultaneously able to be forwarded and evaluated by therespective bus subscriber or the master module.

During the initialization of the bus system, the bus system may beconfigured to detect the bus subscriber that is most remote from themaster module. This bus subscriber is adapted to automatically close thebus system. This relieves the operator of the bus system inasmuch as theoperator does not have to connect a terminating impedance within thesystem. The security is therefore improved.

The bus system may include at least one first data line and one seconddata line. This offers the advantage that a data packet is able to besent from the master module to the bus subscribers with the aid of thefirst data line, and a data packet is able to be sent from a respectivebus subscriber to the master module with the aid of the second dataline, in particular at the same time. The speed of the data transmissionis thus increased and the security improved. For the closing of the bussystem, the last bus subscriber may connect the first data line to thesecond data line, in particular short-circuits them. The bus system maybe arranged as a communications ring.

A data packet may be transmittable from the master module to the bussubscribers using the first data line. This has the advantage that thefirst data line and the second data line may be disposed in parallel.Data packets may be transmittable at any time from the master module tothe bus subscribers using the first data line. As a result, the datatransmission from the master module to the bus subscribers will not beinterrupted for the transmission of a respective data packet from anindividual bus subscriber to the master module.

The respective data line may have at least one data cable in each case,and each bus subscriber may be connected by a respective data cable tothe bus subscriber upstream or downstream from it or to the mastermodule. This has the advantage that the respective data line may have amodular configuration. As a result, a further bus subscriber is easilyconnected to the bus system with the aid of a further data cable.

Each data cable may have two mating plug connector parts and each bussubscriber may have a first plug connector part for the connection tothe respective upstream bus subscriber with the aid of an individualdata cable, and each bus subscriber may have a second plug connectorpart for the connection to the respective downstream bus subscriber.This has the advantage that the bus subscribers of the bus system areeasily connected to each other in a reversible manner. As a result, afurther bus subscriber is easily connectable to the bus system, or a bussubscriber is easily separable from its upstream bus subscriber and/orfrom its downstream bus subscriber.

The respective data cable of the first data line and the respective datacable of the second data line may be disposed between two adjacent bussubscribers in a cable sheath, the cable sheath in particularsurrounding the data cables in the circumferential direction, inparticular enveloping them. This has the advantage of reducing thewiring expense. The first and the second data line may be connected by ashared plug connector part so that only one plug connector part has tobe plugged into the bus subscriber in order to connect a bus subscriberto its upstream or downstream bus subscriber. The plug connection may beimplementable in a manner that prevents a polarity reversal.

A supply line and/or a ground lead for the bus subscribers maybedisposed in the cable sheath. This has the advantage of reducing thewiring expense. The data cables and the supply line and/or the groundlead may be connected to a shared plug connector part so that only oneplug connector part has to be plugged into the bus subscriber in orderto connect a bus subscriber to its upstream or downstream bussubscriber. The plug connection may be implementable in a manner thatprevents a polarity reversal.

Each bus subscriber may have a switch, which is connected to arespective data line, the switch being arranged to interrupt the datatransmission along the respective data line. This has the advantage thatthe individual bus subscriber is arranged to use the switch to stop datapackets that are not meant to reach the master module. In this manner,the bus subscriber relieves the loading of the master module.

Each bus subscriber may have a time-measurement device. This has theadvantage that the time-measurement device allows the individual bussubscriber to measure a time span within which a further bus subscriberresponds to a data packet, and in particular sends a further datapacket. The further data packet is thus able to be evaluated as afunction of this time span, in particular is able to be blocked by theswitch. This relieves the loading of the master module.

Each bus subscriber may have a logic circuit, and the logic circuit inparticular may make it possible to evaluate data packets of the mastermodule and/or of the bus subscribers. This offers the advantage that theswitch and/or the time-measurement device is/are able to be actuatedwith the aid of the logic circuit, in particular as a function of a datapacket.

The respective logic circuit may have a storage device, which may beused for storing data packets. As a result, a data packet that wasstopped by a bus subscriber may be stored by its storage device and betransmitted to the master module and/or to a bus subscriber at a laterpoint in time.

The emergency signal may be able to be detected with the aid of thelogic circuit, and the emergency signal may be forwarded to an adjacentbus subscriber simultaneously with the further evaluation of theemergency signal. This is considered advantageous insofar as theemergency signal is able to be forwarded without delay so that a rapidshutdown of all bus subscribers of the bus system is possible. Thisincreases the security.

Each bus subscriber may have an electronic circuit, the electroniccircuit including the switch and/or the time-measurement device and/orthe logic circuit, the switch and/or the time-measurement device and/orthe logic circuit in particular being integrated into the electroniccircuit. This has the advantage that the electronic circuit may have acompact and secure configuration.

Further features and aspects of example embodiments of the presentinvention are described in greater detail below with reference to theappended Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a bus system according to an exampleembodiment of the present invention.

FIG. 2 shows the time characteristic of data packets (3, 4) on a databus.

FIG. 3 shows the time characteristic of data packets (3, 4) and anemergency signal on the data bus in a first case example.

FIG. 4 shows the time characteristic of data packets (3, 4) and anemergency signal on the data bus in a second case example.

DETAILED DESCRIPTION

The bus system according to an example embodiment of the presentinvention has a master module M and bus subscribers (S1, S2, S3, S4),which are disposed in series and connected to one another. The bussystem has a first bus subscriber S1 disposed downstream from mastermodule M. The bus system has a second bus subscriber S2 disposeddownstream from first bus subscriber S1, first bus subscriber S1 beingsituated upstream from second bus subscriber S2. Second bus subscriberS2 is disposed upstream from a third bus subscriber S3, and third bussubscriber S3 is situated downstream from second bus subscriber S2.Third bus subscriber S3 is disposed upstream from a fourth bussubscriber S4, and fourth bus subscriber S4 is disposed downstream fromthird bus subscriber S3.

A bus subscriber (S1, S2, S3, S4) situated downstream from another bussubscriber (S1, S2, S3, S4) is situated at a greater distance frommaster module M than the other bus subscriber (S1, S2, S3, S4) in thedirection of the series arrangement. The other bus subscriber (S1, S2,S3, S4), which is disposed at a shorter distance from master module Mthan the bus subscriber (S1, S2, S3, S4) in the direction of the seriesarrangement, is located upstream from the bus subscriber (S1, S2, S3,S4).

For example, the bus system is an industrial plant that has variousdevices as bus subscribers (S1, S2, S3, S4), such as drives orelectronic components, e.g., drive converters for electric motors.

The data bus has a first data line 1 and a second data line 2, which ineach case serially connect the bus subscribers (S1,S2, S3, S4) andmaster module M to one another.

With the aid of first data line 1, master module M sends data packets(3, 4) such as control commands to the bus subscribers (S1, S2, S3, S4).With the aid of second data line 2, the bus subscribers (S1, S2, S3, S4)send data packets (3, 4) such as status information to master module M.

Each bus subscriber (S1, S2, S3, S4) has a first interface and a secondinterface, which are, for example, arranged as plug connector parts ineach case. Each data line (1, 2) has at least one data cable. Each datacable has a first mating plug connector part and at least one secondmating plug connector part for a data transmission between the bussubscribers (S1,S2, S3, S4) along the respective data line (1, 2).

As a result, each bus subscriber (S1, S2, S3, S4) is able to beconnected to a second plug connector part of an upstream bus subscriber(S1, S2, S3, S4) using a first plug connector part and the respectivedata cable, and is able to be connected by a second plug connector partand the respective data cable to a first plug connector part of adownstream bus subscriber (S1, S2, S3, S4).

The respective data cable of first data line 1 and the respective datacable of second data line 2 may be guided in a shared cable sheath. Asupply line and/or a ground lead for the bus subscribers (S1, S2, S3,S4) may be disposed in this cable sheath as well.

Each bus subscriber (S1, S2, S3, S4) has a switch, in particular anelectronic circuit, which is connected to the respective data line (1,2). The switch may be used to interrupt the data transmission along therespective data line (1, 2).

Each bus subscriber (S1, S2, S3, S4) has a time-measurement device, inparticular a timer. The time-measurement device maybe integrated intothe electronic circuit of the bus subscriber (S1, S2, S3, S4).

Using the electronic circuit, the data transmission along the respectivedata line (1, 2) is therefore able to be interrupted after a predefinedtime has elapsed.

Each bus subscriber (S1, S2, S3, S4) has a logic circuit. The logiccircuit may be integrated into the electronic circuit of the bussubscriber (S1, S2, S3, S4).

Using the logic circuit, data packets on the data bus are able to beevaluated, and the sender of a data packet, in particular, isidentifiable.

In the event that a bus subscriber (S1, S2, S3, S4) is inactive, a datapacket (3, 4) is forwarded without interruption and without a time delaythrough the inactive bus subscriber (S1, S2, S3, S4) to the downstreamor upstream bus subscriber (S1, S2, S3, S4). A data packet (3, 4) passesthrough an inactive bus subscriber (S1, S2, S3, S4) without obstruction.

The data bus may be implemented in a digital form.

For the initialization of the bus system, master module M sends arequest to log in to master module M to the bus subscribers (S1, S2, S3,S4) situated downstream. An active bus subscriber (S1, S2, S3, S4)disposed downstream from master module M logs in to master module M andforwards the request for the login to master module M to bus subscribers(S1, S2, S3, S4) downstream from it. The logged in bus subscriber (S1,S2, S3, S4) then waits for a predefined period of time to see whether abus subscriber (S1, S2, S3, S4) downstream from it logs in to mastermodule M.

If no downstream bus subscriber (S1, S2, S3, S4) logs in to the mastermodule, then the last logged in bus subscriber (S1,S2, S3, S4) closesthe bus system as soon as the predefined period of time has elapsed, byconnecting first data line 1 and second data line 2 to each other, inparticular short-circuiting them. A data packet (3, 4) that istransmitted with the aid of first data line 1 from master module M tothe bus subscribers (S1, S2, S3, S4) is thus forwarded to second dataline 2 at the final bus subscriber (S1, S2, S3, S4) and routed back tothe master module.

The last bus subscriber (S1, S2, S3, S4) is the particular bussubscriber (S1, S2, S3, S4) that logs in last to master module M and hasno active downstream bus subscribers (S1, S2, S3, S4).

The request to log in to master module M is routed through an inactivebus subscriber (S1, S2, S3, S4) without this subscriber itself loggingin to master module M.

After the bus system has been closed, a release is granted by asuperordinate control or by an operator and the bus system begins itsoperation.

In the event that a bus subscriber (S1, S2, S3, S4) logs in late, i.e.after the predefined period of time following the login of the last bussubscriber (S1, S2, S3, S4) has elapsed, then this bus subscriber (S1,S2, S3, S4) sends a data packet (3, 4) to master module M. If a releasehas already been granted, this data packet (3, 4) is stopped by anupstream bus subscriber (S1, S2, S3, S4) that is logged in to mastermodule M and is not forwarded to master module M.

As soon as the release has been revoked, a data packet (3, 4)of the latebus subscriber (S1, S2, S3, S4) is forwarded to master module M and thelate bus subscriber (S1, S2, S3, S4) is admitted to the bus system.

In the event that the late bus subscriber (S1, S2, S3, S4) has nodownstream bus subscribers (S1, S2, S3, S4) that are logged in to mastermodule M, then it becomes the new last bus subscriber (S1, S2, S3, S4)and closes the bus system after waiting out the predefined period oftime for the login of a bus subscriber (S1, S2, S3, S4).

The predefined period of time for the login of a bus subscriber (S1, S2,S3, S4) is able to be adapted to the bus subscribers (S1, S2, S3, S4).The period of time may be selected such that bus subscribers (S1, S2,S3, S4) that have a longer initialization time are securely logged in tomaster module M.

During the initialization of the bus system, bus addresses for the bussubscribers (S1, S2, S3, S4) are assigned automatically. For thispurpose, master module M sends the bus address “1” to first bussubscriber S1. First bus subscriber S1 logs in to master module M usingthis bus address and increments the bus address by 1 and forwards it toits downstream bus subscriber (S1, S2, S3, S4). The downstream bussubscriber (S1, S2, S3, S4) logs in to master module M using theincremented bus address, i.e. bus address “2” in this instance,increments this bus address by 1 again and forward sit to the bussubscriber (S2, S3, S4) downstream from it.

In an effort to restrict the number of bus subscribers (S1, S2, S3, S4)in the bus system, a bus subscriber (S1, S2, S3,S4) assigned a busaddress that is greater than the maximally allowed number of bussubscribers (S1, S2, S3, S4) will not further increment this bus addressbut forwards the same bus address to its downstream bus subscriber (S1,S2, S3, S4), which uses this bus address to log in to master module M.As soon as master module M receives a bus address that is greater thanthe maximally allowed number of bus subscribers (S1, S2, S3, S4), mastermodule M aborts the initialization of the bus system and transmits anerror report to a control superordinate to master module M.

If a bus subscriber (S1, S2, S3, S4) that is not yet active, i.e. aninactive bus subscriber (S1, S2, S3, S4), receives a bus address from abus subscriber (S1, S2, S3, S4) upstream from it or from master moduleM, then this bus address is looped through the inactive bus subscriber(S1, S2, S3, S4) without being incremented, and assigned to a downstreambus subscriber (S1, S2, S3, S4).

FIGS. 2 through 4 show the time characteristic of data packets 3 thatare transmitted with the aid of a respective data line (1, 2). Each datapacket 3 has a predefined length that is a function of the number of bussubscribers (S1, S2,S3, S4) of the bus system.

The data transmission is interrupted for a predefined period of timebetween two temporally successive data packets 3, which means that twotemporally successive data packets 3 are temporally spaced apart withthe aid of a transmission pause 6.

As soon as a bus subscriber (S1, S2, S3, S4) or master module M detectsan error, data packet 4 transmitted at that instant is immediatelyinterrupted and an emergency signal 5 is transmitted by the respectivebus subscriber (S1, S2, S3, S4)or by master module M, as illustrated inFIG. 3. This emergency signal 5 causes an immediate shutdown of all bussubscribers (S1, S2, S3, S4).

The interrupted data packet 4 is immediately terminated and not furtherprocessed by the bus subscribers (S1, S2, S3, S4).

If a bus subscriber (S1, S2, S3, S4) or master module M detects an errorduring a transmission pause 6, then transmission pause 6 will beinterrupted and an emergency signal 5 be sent by the respective bussubscriber (S1, S2, S3,S4) or by master module M, as illustrated in FIG.4. This emergency signal 5 causes an immediate shutdown of all bussubscribers (S1, S2, S3, S4).

The respective bus subscriber (S1, S2, S3, S4) transmits emergencysignal 5 on both data lines (1, 2). In other words, emergency signal 5is transmitted from the respective bus subscriber (S1, S2, S3, S4) inthe direction of master module M on the second data line and istransmitted from the respective bus subscriber (S1, S2, S3, S4) awayfrom master module M on first data line 1.

The respective bus subscribers (S1, S2, S3, S4) immediately process theemergency signal 5 and at the same time forward it to the downstream bussubscriber (S1, S2, S3, S4) so that the bus subscribers (S1, S2, S3, S4)shut down immediately. In other words, emergency signal 5 is not firststored and processed but immediately forwarded to all bus subscribers(S1, S2, S3, S4) and to master module M.

The emergency signal 5 may have a temporally shorter length, inparticular signal length, than the data packets (3, 4) and/ortransmission pause 6.

LIST OF REFERENCE CHARACTERS

M master module

S1 first bus subscriber

S2 second bus subscriber

S3 third bus subscriber

S4 fourth bus subscriber

1 first data line

2 second data line

3 data packet

4 data packet

5 emergency signal

6 transmission pause

What is claimed is:
 1. A bus system, comprising: a master module; andbus subscribers arranged in series between the master module and a lastone of the bus subscribers, a single first bus subscriber being arrangedimmediately downstream of the master module, each bus subscriber betweenthe first bust subscriber and the last bus subscriber having a singleone of the bus subscribers being arranged immediately upstream and asignal one of the bus subscribers being arranged immediately downstream;wherein each bus subscriber arranged between the first bus subscriberand the last one of the bus subscribers is adapted to receive anemergency signal transmitted by a first immediately adjacent bussubscriber, to immediately forward the emergency signal to a secondimmediately adjacent bus subscriber, and to automatically shut down inresponse to the emergency signal.
 2. The bus system according to claim1, wherein the first bus subscriber is adapted to receive the emergencysignal from the master module, to immediately forward the emergencysignal to a second bus subscriber, and to automatically shut down inresponse to the emergency signal.
 3. The bus system according to claim1, wherein the master module is adapted to receive the emergency signalfrom the first bus subscriber and to automatically shut down in responseto the emergency signal.
 4. The bus system according to claim 1, whereinthe last one of the bus subscribers is adapted to receive the emergencysignal from an immediately adjacent bus subscriber and to automaticallyshut down in response to the emergency signal.
 5. The bus systemaccording to claim 1, wherein each bus subscriber between the first bussubscriber and the last one of the bus subscribers is connected to anupstream immediately adjacent bus subscriber by a first data line and toa downstream immediately adjacent bus subscriber by a second data line.6. The bus system according to claim 1, wherein the first bus subscriberis connected to the master module by a first data line and a downstreamimmediately adjacent bus subscriber by a second data line.
 7. The bussystem according to claim 1, wherein the last one of the bus subscribersis connected to an upstream immediately adjacent bus subscriber by asecond data line.
 8. The bus system according to claim 5, wherein thefirst data line and the second data line include plug connectorsconnected to respective bus subscribers.
 9. The bus system according toclaim 1, wherein each bus subscriber is adapted to detect an errorstatus and to transmit the emergency signal in response to the detectionof the error status.
 10. The bus system according to claim 1, whereinthe master module is adapted to detect an error status and to transmitthe emergency signal in response to the detection of the error status.11. The bus system according to claim 1, wherein the bus subscribersinclude a drive, an electronic component, and/or a drive converter foran electric motor.
 12. The bus system according to claim 1, wherein eachbus subscriber includes an electronic circuit adapted to interrupt adata transmission to at least one immediately adjacent bus subscriber.13. The bus system according to claim 1, wherein the master module isadapted to send a request to the first bus subscriber to log in to themaster module, and the first bus subscriber is adapted to log in to themaster module in response to the request and to forward the request toan immediately adjacent downstream bus subscriber.
 14. The bus systemaccording to claim 13, wherein each bus subscriber downstream of thefirst bus subscriber and between the first bus subscriber and the lastone of the bus subscribers is adapted to log in to the master module inresponse to the request and to forward the request to an immediatelyadjacent downstream bus subscriber.
 15. The bus system according toclaim 14, wherein the last one of the bus subscribers is adapted to login to the master module in response to the request.
 16. The bus systemaccording to claim 1, wherein the master module is adapted to assign abus address to the first bus subscriber, and each bus subscriber betweenthe first bus subscriber and the last one of the bus subscribers isadapted to increment an assigned bus address and forward the incrementedbus address to a downstream immediately adjacent bus subscriber.
 17. Thebus system according to claim 16, wherein the first bus subscriber isadapted to log in to the master module with the assigned bus address andeach other bus subscriber is adapted to log in to the master module witha respective incremented bus address.
 18. The bus system according toclaim 1, wherein the master module is adapted to connect to apredetermined maximum number of bus subscribers.
 19. The bus systemaccording to claim 18, wherein the master module is adapted to abort aninitialization of the bus system in response to receiving a log inrequest from a bus subscriber exceeding the predetermined maximum numberof bus subscribers.
 20. The bus system according to claim 9, whereineach bus subscriber is adapted to interrupt a data transmission and/or apause in a data transmission in response to the detection of the errorstatus and to transmit the emergency signal in response to the detectionof the error status after the interruption of the data transmissionand/or the pause in the data transmission.